To a solution of dimethyl (2S,3S,5S)-5-tert-butoxy-2-[(4-phenylpiperazin-1-yl)carbonyl]piperidine-1,3-dicarboxylate (0.038 g, 0.000082 mol) in methanol (0.30 mL, 0.0074 mol) was added 1.640 M of N-hydroxyamine in methanol (1.004 mL), freshly made from the corresponding hydroxylamine HCl salt and sodium methoxide. The mixture was stirred at rt for 1 h then acidified with 1N HCl. The resulting mixture was applied directly on RP-HPLC to give the targeted product as a TFA salt (10 mg, 45%). MS (ESI): (M+H)+=463.2.
